The measurement of time, the measurement of the constant of change, is very different than our experience of time. For example, you never experienced a past, you experienced Now measured as the Present, just as you are currently experiencing Now measured as the Present, and will not experience the future, it will be Now measured as the Present. All you have ever experienced is a perpetual fixed Now. This is true for all of us. All measurements of time occur within a fixed Now, so we can say all time is Now.
Depending on certain spiritual views, what we call the Now is also called the “I Am”, or consciousness, or awareness, etc. This “I Am” is intangible and exists outside of time, therefore, depending on your spiritual beliefs, you are the object, existing in a place outside of time, and are already there, and have never left.
For #1 "Can God kill Himself.?"This presumes God is a physical and material being. If God is a non material being, not consisting of matter, then God was never born, as no material substance was brought into being, therefore God cannot die. So the answer would be no, because God was never born.
For #2 “Can God create a stone he cannot lift?” No. If God is a non material being, that creates the potential for material objects, then God would presumably create the potential of the material stone, and then the potential for a material being, that God could then animate through consciousness. God would then be both a non material being, and a material being in which he animates, that has the potential to lift the stone. Now if you belive that every material object has consciousness, then God would be the being lifting the stone, and the stone itself, so in essence God would be lifting Himself.
For #3 “Can God create a square circle?” Yes. God is a non material being that creates the potential for material objects, form and shape. The measurement of these shapes are arbitrary, measured by material beings, of form and shape. The circle and the square are the same object, a shape, only differentiated by a distribution of points, where one object can configure itself to be the same shape as the other object, by redistributing each objects respective points. So can God create the potential of a shape that can reconfigure itself into another shape, Yes.
Think of it like this, say you have a group of nanobots that are positioned in such a way that they form a shape that we label a circle. Then those nanobots reposition themselves into a shape, that we label as a square. Now did those nanobots create 2 different shapes, or a single shape that reconfigures itself? If it’s just a shape that reconfigured itself, then the shape is neither a square nor a circle, it’s just simply a shape, that is arbitrarily measured, whose measurement does not change the fact that what is being measured is still just a shape.